1. Technical Field
The present invention relates to a printed circuit board and a method for manufacturing the same.
2. Description of the Related Art
Technical development for size and weight reduction, and thinner and simpler configuration of an electronic apparatus such as a laptop computer, a net-book, a tablet PC, a smart phone, a navigator, and the like has remarkably increased. Technologies for size and weight reduction, and thinner and simpler configuration of an electronic apparatus require not only techniques of decreasing the size of electronic components mounted on the electronic apparatus and micro-processing the same but also design techniques for optimizing a mounting space. Especially, a printed circuit board enabling high density and high integration mounting of electronic components thereon is essentially demanded.
Single-sided printed circuit boards, double-sided printed boards and multilayer printed circuit boards are currently manufactured and available on the market.
The multilayer printed circuit board is configured by laminating a plurality of single-sided boards wherein a specific conductive material is embedded in an internal layer to increase a mounting density of electronic components while improving variation in electrical characteristics, thus being preferably employed.
For production of a multilayer printed circuit board (‘PCB’), in order to protect internal circuits against surrounding conditions and maximize interlayer adhesion during lamination to combine respective internal and external layers, thus securing the reliability of the PCB, a variety of surface treatment processes have been conducted.
FIG. 1 is a schematic view illustrating a surface of an internal circuit surface-treated by a conventional brown oxide treatment method through acid type etching.
Referring to FIG. 1A, a PCB 10 has copper (Cu) patterns 12 as an internal circuit formed on both sides of an insulating layer 11. When the Cu patterns 12 are surface treated by brown oxide treatment, an anchor type surface roughness 12a and an organic layer 13 are formed on a surface of the Cu patterns 12, as shown in FIG. 1B.
FIG. 2 is a schematic view illustrating a surface of an internal circuit surface-treated by a conventional alkali reduction type black oxide treatment process.
Referring to FIG. 2A, a PCB 20 has Cu patterns 22 as an internal circuit formed on both sides of an insulating layer 21. When the Cu patterns 22 are surface treated by black oxide treatment using an oxidizing agent and an alkali material, a black oxide layer 23 in a needle structure containing Cu(II) oxide and Cu(I) oxide is formed on a surface of the surface-treated Cu patterns 22a, as shown in FIG. 2B. Moreover, as shown in FIG. 2C, a post-dipping process using a reducing agent and an alkali material is carried out to enable reduction of a surface of the black oxide layer 23 while maintaining the needle structure thereof, thereby forming a Cu reduction layer 24.
FIG. 3 is a schematic view illustrating a surface of an internal circuit surface-treated by a conventional black oxide treatment method through acid dissolution.
Referring to FIG. 3A, a PCB 30 has Cu patterns 32 as an internal circuit formed on both sides of an insulating layer 31. When the Cu patterns 32 are surface treated by a black oxide treatment method, a black oxide layer 33 in a needle structure containing Cu(II) oxide and Cu(I) oxide is formed on a surface of the surface-treated Cu patterns 32a, as shown in FIG. 3B. Moreover, as shown in FIG. 3C, a post-dipping process using an acidic dissolving agent is carried out to form a Cu(I) oxide layer 34 wherein a needle structure is converted into a micro-granular structure.
For products manufactured by the foregoing surface treatment processes, an epoxy based interlayer bonding resin (often referred to as ‘prepreg’) having a low glass transition temperature Tg (less than 140° C.) and a high resin impregnation rate has generally been used.
However, with the rapidly growing technologies in electronics as described above, a high reliability material used for manufacturing an electronic product with high density, high integration, ultrathin film and high economical efficiency is also required.
As for lamination of products treated by a conventional brown oxide treatment or black oxide treatment method, a variety of prepregs having specific characteristics such as a normal Tg (less than about 140° C.), a middle Tg (about 150 to 170° C.), a high Tg (more than about 180° C.), a low dielectric constant (Dk; less than about 4.2), a low dielectric loss (Df; less than about 0.015) and/or halogen-free properties (including antimony-free or red phosphorous-free properties) are generally used. For instance, when a bismaleidotriazine (BT) resin having a Tg of more than 200° C., excellent characteristics such as heat resistance, dielectric properties, insulating properties and/or migration-resistance, and favorable activity under molding conditions is used as a prepreg for manufacturing a semiconductor packaging substrate, the substrate treated by a conventional brown oxide treatment or black oxide treatment method has a peel strength of about 0.2 kgf/cm, which is not suitable for a high reliability product requiring a peel strength of at least 0.4 kgf/cm.
In particular, if a black-oxide treatment process is conducted in a horizontal roll type line, a substrate may have numerous roll marks generated on a surface thereof, which in turn causes Cu exposure, thus causing problems in interlayer adhesion and appearance of a final product.